LATENCY(1) BSD General Commands Manual LATENCY(1)NAMElatency — monitors scheduling and interrupt latencySYNOPSISlatency [-p] [-h] [-m] [-st threshold] [-it threshold] [-c code_file]
[-l log_file] [-R raw_file] [-n kernel]
DESCRIPTION
The latency utility provides scheduling and interrupt-latency statistics.
Due to the kernel tracing facility it uses to operate, the command
requires root privileges.
The arguments are as follows:
-c code_file
When the -c option is specified, it takes a path to a code file
that contains the mappings for the system calls. This option
overrides the default location of the system call code file,
which is found in /usr/share/misc/trace.codes.
-h Display high resolution interrupt latencies and write them to
latencies.csv (truncate existing file) upon exit.
-m Display per-CPU interrupt latency statistics.
-it threshold
Set the interrupt latency threshold, expressed in microseconds.
If the latency exceeds this value, and a log file has been speci‐
fied, a record of what occurred during this time is recorded.
-l log_file
Specifies a log file that is written to when either the interrupt
or scheduling latency is exceeded.
-n kernel
By default, latency acts on the default /mach_kernel. This
option allows you to specify an alternate booted kernel.
-p priority
Specifies the priority level to observe scheduler latencies for.
-st threshold
Set the scheduler latency threshold in microseconds. If latency
exceeds this, and a log file has been specified, a record of what
occurred during this time is recorded.
-R raw_file
Specifies a raw trace file to use as input.
The data columns displayed are as follows:
SCHEDULER The number of context switches that fall within
the described delay.
INTERRUPTS The number of interrupts that fall within the
described delay.
The latency utility is also SIGWINCH savvy, so adjusting your window
geometry will change the list of delay values displayed.
SAMPLE USAGElatency-p 97 -st 20000 -it 1000 -l /var/tmp/latency.log
The latency utility will watch threads with priority 97 for scheduling
latencies. The threshold for the scheduler is set to 20000 microseconds.
The threshold for interrupts is set to 1000 microseconds. Latencies that
exceed these thresholds will be logged in /var/tmp/latency.log.
SEE ALSOfs_usage(1), sc_usage(1), top(1)Mac OS X March 28, 2000 Mac OS X
